CROSS-REFERENCE(S) TO RELATED APPLICATIONS

This application claims priority to South African provisional patent application number 2014/00160, which is incorporated by reference herein.

FIELD OF THE INVENTION

This invention relates to liquid pumps and, more particularly, it relates to liquid pumps in which the pumping action is assisted by gravity.

BACKGROUND TO THE INVENTION

Aquaculture, also known as aquafarming, is the farming of aquatic organisms such as fish, crustaceans, molluscs and aquatic plants. In 2004, the total world production of fisheries was approximately 140 million tonnes of which aquaculture contributed approximately 45 million tonnes. The growth rate of worldwide aquaculture has been sustained and rapid, averaging about 8 percent per annum for over thirty years and global aquaculture production reached a record high of more than 90 million tons in 2012. Land-based aquaculture facilities generally comprise a number of fairly large tanks in which the aquatic organisms are grown. Seawater is continuously circulated through the tanks and then either returned to the ocean or cleaned and returned to the tanks. In this regard, and using conventional techniques, a fish farm requires about 1 litre/second seawater supply per ton of production per annum, while a molluscs farm, such as an abalone farm, requires about 5 litres/second seawater per ton of production per annum.

In South Africa, the cost of electricity to lift 1 cubic meter of seawater to a location 30 meters above sea level is approximately 0.10 South African Rand (ZAR), assuming an 80% efficiency rate of the pump. Thus, in order to supply a 100 ton per annum fish farm at an altitude of 30 meters above sea level, the annual electricity cost to pump the water is approximately ZAR 315,000.00, while the cost of electricity to supply a 100 ton per annum abalone farm is approximately ZAR 1 ,575,000.00. The constant need of seawater supply and resultant cost of electricity, dictates that aquaculture facilities are located in close proximity to the ocean so as to maintain electricity consumption at a minimum. However, lower level sites are generally more environmentally sensitive, causing the planning and initial setup of such facilities to take longer and be more costly. In addition, appropriate land is typically in short supply resulting in higher cost thereof. Also, lower sites are typically more at risk from storms and rising tides.

SUMMARY OF THE INVENTION

In accordance with the invention there is provide a gravitationally assisted liquid pump assembly for pumping a liquid from a liquid supply at a lower level to a relatively elevated reservoir located at a level higher than the pump assembly, the pump assembly comprising a variable volume supply chamber in communication with a supply conduit for supplying a volume of liquid from the supply chamber to the elevated reservoir and a return conduit for returning a volume of liquid from the elevated reservoir to a variable volume return chamber wherein the volume of the variable volume supply chamber and the volume of the variable volume return chamber interact to ensure that a decrease in the volume of the variable volume supply chamber occasioned by flow of liquid to the reservoir is substantially equal to the volume of liquid returned from the reservoir to the variable volume return chamber so that pressure generated by the weight of liquid in the return conduit is transferred to the liquid in the variable volume supply chamber, at least to some extent, to at least partially balance the weight of liquid in the supply conduit; a pump in either or both of the supply and return conduits for pumping liquid into or out of the reservoir, an arrangement of flow valves for cyclically reversing the direction of flow of liquid into and out of the variable volume supply and return chambers when one is substantially full and the other is substantially empty, and an arrangement for introducing supply liquid into the variable volume supply chamber.

Further features of the invention provide for the supply conduit and return conduit to communicate with the supply chamber and return chamber at remote positions relative to the two chambers; for the supply chamber and return chamber to be separated by one or more pistons or a flexible diaphragm either within a single enclosure or in two separate enclosures in which instance a mechanical or fluid coupling is provided to ensure reciprocal increase and decrease in the variable volume of the supply chamber and the return chamber; in the alternative, for the supply chamber and return chamber to be interconnected with the supply conduit and return conduit communicating with the single chamber in a manner selected to minimise mixing of the return liquid and supply liquid with no physical separator between the supply chamber and the return chamber; for the arrangement of flow valves to include one or more unidirectional valves to ensure unidirectional flow through the supply conduit and return conduit; for the arrangement for introducing supply liquid into the supply chamber to be a pump interposed between the liquid supply and the supply chamber; and for the entire gravitationally assisted pump assembly to be located below, at, or a small distance above a liquid supply level such that a major part of the supply conduit and return conduit extend between the supply and return chambers and the reservoir.

Yet further features of the invention provide for the assembly to include overflow conduits that are in communication with the supply chamber and return chamber; for the overflow conduits to include sensors which sense when liquid is introduced into the overflow conduits thereby indicating that the volume of liquid supplied from the supply chamber and the liquid returned to the return chamber are not substantially equal; and for the sensors to be capable of modifying the flow of liquid into the supply chamber and/or returned to the return chamber so as ensure that the volumes are substantially equal. BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described, by way of example only, with reference to the accompanying representations in which: Figure 1 is a schematic illustration of a first embodiment of gravitationally assisted liquid pump assembly according to the invention with the flow valves in a position corresponding to the supply chamber filling with supply water from a liquid supply;

Figure 2 is a schematic illustration of the first embodiment of the invention illustrated in Figure 1 with the flow valves reversed in position and corresponding to return water entering the return chamber;

Figure 3 is a schematic illustration of a second embodiment of gravitationally assisted liquid pump assembly according to the invention in which two supply chambers and two return chambers are provided in which a second supply chamber is in communication with the supply conduit;

Figure 4 is a schematic illustration of the second embodiment of the invention in which a first supply chamber is in communication with the supply conduit; Figure 5 is a schematic illustration of a third embodiment of a gravitationally assisted liquid pump assembly according to the invention, in which a freely longitudinally movable divider separates the supply and return chambers;

Figure 6 is a schematic illustration of a fourth embodiment of the invention in which no divider is provided between the supply chamber and the return chamber in which the supply chamber is filling up;

Figure 7 is a schematic illustration of the fourth embodiment of the invention in which the supply chamber is in communication with the supply conduit; and

Figure 8 is a schematic illustration of the fifth embodiment of the invention in which only one pump is utilized. DETAILED DESCRIPTION WITH REFERENCE TO THE DRAWINGS

Figures 1 and 2 illustrate a first embodiment of a gravitationally assisted liquid pump assembly (10) for pumping a liquid from a liquid supply (12) at a lower level, in this embodiment the ocean, to a relatively elevated reservoir (14) located at a level higher than the assembly (10). The assembly (10) includes a variable volume supply chamber (16) in communication with a supply conduit (18) for supplying a volume of liquid from the supply chamber (16) to the elevated reservoir (14), and a variable volume return chamber (20) in communication with a return conduit (22) for returning a volume of liquid from the elevated reservoir (14) to the return chamber (20). The volume of the supply chamber (16) and the return chamber (20) interact with each other so as to ensure that a decrease in the volume of the supply chamber (1 6) occasioned by flow of liquid to the reservoir (14) is substantially equal to the volume of liquid returned from the reservoir (14) to the return chamber (20). In the embodiment illustrated in Figure 1 , the supply chamber (16) and return chamber (20) are interconnected to form a single enclosure (21 ), with the volumes of liquid in the chambers (16, 20) being separated by a flexible diaphragm (24) so as to ensure that the liquid supplied from the supply chamber (16) and the liquid returned to the return chamber (20) do not mix. In order to introduce a volume of liquid cyclically into the supply chamber (16), the assembly (10) further includes an arrangement, in this embodiment a primary pump (26) interposed between the supply chamber (16) and the liquid supply (12).

The assembly (1 0) further includes a secondary pump (28) in the supply conduit (18) for pumping liquid from the supply chamber into the reservoir (14). In addition, a supply flow valve (30) and a return flow valve (32) are provided for cyclically reversing the direction of flow of liquid into and out of the supply chamber (16) and return chamber (20) when one is substantially full and the other substantially empty. In the embodiment illustrated, the supply conduit (18) includes a supply flow valve (30) which is arranged to either direct liquid pumped from the liquid supply (12) into the supply chamber (16), or direct liquid from the supply chamber (16) into the supply conduit (18) and into the reservoir (14). It will be appreciated that the supply flow valve (30) may also comprise a number of control and non-return valves that operate in unison. The return conduit (22) includes a return flow valve (32) which is arranged to either permit liquid to flow from the reservoir (14) into the return chamber (20) during the time that liquid is leaving the supply chamber to flow up through the supply conduit into the reservoir or from the return chamber (20) back to waste during times when the supply chamber is being filled from the liquid supply.

In use, and as illustrated in Figure 1 , during a first cycle, the supply flow valve (30) regulating flow of liquid into or out of the supply chamber (16) is arranged to permit liquid to be pumped from the liquid supply (12) into the supply chamber (16), while the return flow valve (32) regulating flow of liquid into or out of the return chamber (20) is arranged to permit liquid to flow from the return chamber to waste that may be a remote part of the liquid supply (12). The liquid introduced into the supply chamber (16) causes the volume of the supply chamber (16) to increase thereby moving the flexible diaphragm (24) and causes the volume of the return chamber (20) to decrease accordingly thereby forcing return liquid out of the return chamber (20).

Once the supply chamber (16) has been filled with a pre-defined volume of liquid, the primary pump (26) is deactivated, and the supply and return flow valves (30, 32) moved so that the supply flow valve (30) liquid directs flow from the supply chamber (16) to the reservoir (14), while the return flow valve (32) directs flow of return liquid into the return chamber (20) as is illustrated in Figure 2. During this procedure, the secondary pump (28) is activated so as to pump liquid from the supply chamber (16) to the reservoir (14). Since the reservoir (14) is located at a level higher than the assembly (10), the weight of the liquid in the return conduit and the return chamber (20) generates a pressure which is transferred, at least to some extent, to liquid in the supply chamber (16) thereby at least partially counter-balancing the weight of liquid held in the supply conduit and the supply chamber (16) and decreasing the energy required of the secondary pump (28).

The transfer of pressure and balancing of weight assists the secondary pump (28) in pumping the liquid from the supply chamber (16) to the reservoir (14) occasioning that a relatively small secondary pump (28) may be utilized to effect pumping of liquid from the supply chamber (16) to the reservoir (14). Similarly, since during the first cycle liquid from the return chamber is permitted to flow to waste, the flow will create a suction thereby assisting the primary pump (26) to pump liquid from the liquid supply (12) into the supply chamber (16) thereby occasioning that a relatively small primary pump (26) may be utilized. The relatively small pump size results in a fairly low electricity consumption, thus reducing the cost of liquid supply to the reservoir when compared to systems where liquid is directly pumped to an elevated reservoir and return liquid is simply allowed to flow freely back to waste. Furthermore, the assembly (10) can be assembled from off- the-shelf pumps, pipes and valves, therefore being relatively low cost to manufacture and maintain.

It will of course be appreciated that in order to ensure an effective transfer of pressure from the return chamber to the supply chamber, the volume of liquid returned from the reservoir must be substantially similar to the volume of liquid supplied to the reservoir. Also, the assembly is preferably located below, at, or a small distance above the liquid supply such that a major part of the supply conduit and return conduit extend between the supply chamber and the reservoir. This is to ensure that the liquid flowing down from the reservoir to the return chamber drops sufficiently in height so that sufficient pressure can be built up to assist in pumping the liquid via the supply conduit to the reservoir.

Once the return chamber (20) has been substantially filled with return liquid and the supply chamber (16) consequently substantially emptied, the flow valves (30, 32) are moved to again permit liquid to be pumped into the supply chamber (16) and to permit liquid to flow out of the return chamber (20), thus starting the cycle afresh.

Figures 3 and 4 illustrate a second embodiment of a gravity assisted liquid pump assembly (50) in accordance with the invention. The assembly (50) of this embodiment functions substantially similarly to the assembly (10) illustrated in Figure 1 , provided that in this embodiment, the assembly includes two supply chambers (52, 54) and two return chambers (56, 58) so as to provide for a more continuous liquid supply.

In use, during a first cycle, a primary pump (60) is activated to pump liquid from the liquid supply to a first supply chamber (52) with the supply flow valve (62) regulating the flow of liquid from the liquid supply into the supply chambers (52, 54) being arranged to permit liquid to flow into the first supply chamber (52). At the same time the supply flow valve permits liquid to flow from the second supply chamber (54) under the action of a secondary pump (66) to the reservoir. At the same time, a return flow valve (68) regulates the flow of return liquid from the return conduit (70) into the return chambers (56, 58) is arranged to permit liquid to flow from the reservoir into the second return chamber (58), while permitting liquid to flow from the first return chamber (56) to waste that may be associated with the liquid supply.

Once the first supply chamber (52) and second return chamber (58) have been substantially filled, and consequently, the second supply chamber (54) and first return chamber (56) substantially emptied, the flow valves (62, 68) are moved and a second cycle commences, as illustrated in Figure 4. In the second cycle, liquid from the first supply chamber (52) is permitted to be pumped to the reservoir while return liquid is received in the co-operating return chamber (56). At the same time liquid is pumped from the liquid supply to the second supply chamber(54), and liquid from the second return chamber (58) is permitted to flow to waste that may be associated with the liquid supply.

Figure 5 illustrates a third embodiment of a gravitationally assisted fluid pump assembly (100) in accordance with the invention. The assembly (100) of this embodiment is again substantially similar to the assembly (10) illustrated in Figure 1 , provided that instead of utilizing a diaphragm to separate the supply chamber (102) from the return chamber (104), a longitudinally freely movable divider (106) made from a neutrally-buoyant material is used. The divider (106) is shaped to slideably engage the sidewalls (108) of the chambers (102, 104) and is moved back and forth during the cyclic pumping of liquid. Since the divider (106) is able to slide in the chambers (102, 104), some mixing of liquid from the supply chamber (102) and the return chamber (104) may take place, yet this will be insignificant in comparison with the volume of liquid being pumped.

Furthermore, where the volume of liquid supplied to the reservoir and the volume of liquid returned from the reservoir are not substantially equal, overflow conduits (1 10, 1 12) may be provided at each chamber (102, 104) so as to ensure that the divider (106) does not move too far to one side. Once the divider (106) moves past the connection (1 14, 1 16) between one of the overflow conduits (1 10, 1 12) and the supply or return chamber (102, 104), liquid will flow into the overflow conduit (1 10, 1 12). Sensors (1 18) may be provided at the overflow conduits (1 10, 1 12) which detect the overflow and cause the volume of liquid pumped by the primary or secondary pump (120, 122) to be adjusted so as to compensate for the imbalance.

Also, in order to be able to pump a large volume of liquid, it is envisaged that several supply and return chambers may be provided in parallel in an assembly (100). Figures 6 and 7 illustrate a fourth embodiment of gravitationally assisted liquid pump assembly (200) in accordance with the invention. The assembly (200) again includes a supply chamber (202) which is in communication with a supply conduit (204) and a return chamber (206) which is in communication with a return conduit (208). In this embodiment, the supply and return chambers (202, 206) are interconnected to from a single elongate sinuous enclosure (209). It will be appreciated that the enclosure may have any suitable shape and could also be straight, spiral or the like. A supply flow valve (210) is provided where the supply conduit (204) and the supply chamber (202) join, while a second flow valve (212) is provided where the return conduit (208) and the return chamber (204) join. Both the supply flow valve (210) and the second flow valve (212) may be provided by a number of control and/or non-return valves. In addition, two pumps (214, 216) are provided, the first pump (214) being utilized to pump liquid to the supply chamber (202) and the second pump (216) to pump liquid from the supply chamber (202) to a reservoir (218).

During a first cycle, and as illustrated in Figure 6, the supply flow valve (210) is arranged so that liquid is pumped into the supply chamber (202) by means of the first pump (214). The return flow valve (212) is simultaneously arranged so that liquid held within the return chamber (206) can flow out of return chamber (206) to waste. The two chambers (202, 206) of this embodiment do not include a mechanical separator in the form of a membrane or the like to separate the liquid in the chambers (202, 206) from each other. Nevertheless, since the volume of liquid introduce into the chambers (202, 206) is substantially equal and due to the shape of the combined chamber, only a minimal amount of mixing occurs. In addition, in order to ensure that liquid from the return chamber (206) is not pumped to the reservoir (216), the assembly may be set up so that slightly more liquid is introduced into the supply chamber (202) than is introduced into the return chamber (206), thereby ensuring that all liquid from the return chamber (206) is forced out prior to the next cycle commencing.

Thus, during a second cycle in which liquid is pumped from the enclosure to the reservoir via the supply conduit and liquid is return to the enclosure from the reservoir via the return conduit, the assembly may be set up so that the liquid being returned to the enclosure only fills the enclosure by approximately 90 percent while maintaining approximately 10 percent of liquid pumped into the enclosure from the liquid supply during the first cycle. Nevertheless, during the first cycle, the enclosure will always be filled 100 percent by liquid pumped from the liquid supply. This will ensure that all liquid introduced into the enclosure from the reservoir is completely removed from the assembly during each cycle. The adjustment in volumes of liquid pumped into and out of the enclosure as described above can be achieved by adjusting the timing of each cycle, i.e. so that the first cycle runs for slightly longer than the second cycle, or by using a more powerful primary pump or throttling the secondary pump.

Also, in order to enable pumping of fairly large volumes of liquid per cycle, the enclosure (209) comprises a number of lengths of piping which are joined together so as to form one long enclosure. Figure 8 illustrates yet a further embodiment of a gravitationally assisted liquid pump assembly (300). The assembly (300) of this embodiment is similar to the embodiment illustrated in Figures 1 and 2, provided that in this embodiment, the assembly (300) includes only one pump (302). The assembly (300) further includes two pairs of flow valves (304, 306) located in the return conduit (308) which may be arranged to cyclically direct the flow of liquid into and out of the return chamber (310). During a first cycle, the first pair of flow valves (304) is open while the second pair of flow valves (306) is closed thereby permitting liquid to be pumped from the reservoir (312) into the return chamber (310). During a second cycle, the first pair of flow valves (304) is then closed while the second pair of flow valves (306) is opened, thereby permitting liquid to be pumped from the return chamber (310) to waste. Since the return chamber (310) and the supply chamber (314) communicate with each other, the pumping of liquid from the return chamber (310) during the second cycle will create a suction in the supply chamber (314) causing liquid to be sucked into the supply chamber (314) from the liquid supply (316). Once the supply chamber (314) has been filled, the first cycle commences again and the liquid pumped into the return chamber (310) will create pressure in the supply chamber (314) which will push the liquid in the supply chamber (314) toward the reservoir (312).

It will be appreciated that many other embodiments of a gravity assisted liquid pump assembly exist which fall within the scope of the invention, particularly regarding the shape and configuration thereof. For example, the assembly will function particularly well for aquaculture facilities since the volume of water returned from the facility is substantially equal to the volume of water pumped up to the facility. In such a case, the assembly could be modified to be able to pump the large amounts of salt water by using corrosion resistant materials, providing filter mechanisms which filter any larger material out prior to the material reaching the pumps and the like. Also, unidirectional or one-way valves may be provided so as to ensure that liquid may flow in one direction only. In addition, since loss of liquid may occur, the assembly may be provided with an additional pump so as to continuously top up the system.